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  1. #1
    Jr. Engineer JTWard's Avatar
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    Question Getting ready for a upgrade project, need advice ?

    I'm going to be swapping out my standard Differential with a "Yukon Dura-Grip" differential. The owners Manual calls for 80W/90 gear oil. How much and what is the best oil/gear oil on the market, It's a brand new differential not a rebuild. I'm not looking to start a fight, just one poor lost soul looking for good advice. Considering royal purple ????? But . .

  2. #2

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    Mobil 1 or royal purple for brand.. Remember this. You get what you pay for. As for fill level, I fill them until I can tough the fluid with the top of my pinky with only the first knuckle bent.
    Chuckie!!!


  3. #3
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    The two oils listed prior to my reply are excellent choices, but Amsoil & Valvoline synthetic are fantastic as well. If you're doing heavy hauling or towing something heavy you can go to a heavier viscosity oil. I used the heavy oil in my truck year round as I plow, tow a bass boat, tow my hot rod on a trailer etc... If I wasn't running a full synthetic gear lube I would go to 80w-90 for the winter and the heavier lube for the summer. With a full synthetic even the heavy gear lube flows well enough to prevent any damage to the bearings from occurring.
    Being as this is a "limited slip" differential" you will also want to buy a bottle of GM limited slip additive. The synthetic oils are adequate without it, but I highly recommend adding it. It is only a few dollars and is maybe 4 ounces. It will prevent "chatter" on tight turns.
    ​Everything in life sucks, except the things that should!

  4. #4
    Jr. Engineer JTWard's Avatar
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    Yeah, the differential is band new, but it comes with Ford Anti-slip oil as the maker of the differential says he's tried all of them, and the Ford Additive is clearly the best, I think it's 4 oz. But I was trying to get 3 qts. Of Royal Purple, but I had to ask a number of questions for him and he got PI*&ed off at me and asked me to stop all the questions ???????

    So I did get some interesting info before he hung up on me, you need to use a gear oil that "Doesn't have too much of the "friction Modifiers" in it. Because your already putting in the GM or Ford friction Modifiers before you finish filling up the differential. So You can get into where the clutches are slipping and not providing the right amount of grip or lubrication or for that matter over lubrication of the clutches. So I looked elsewhere as RP only makes a full synthetic gear oil. But I do run RP motor oil. But I went to Valvoline, and they make a brand a full synthetic, and very basic brand and though it was hard to find, I went with Valvoline "DuraBlend Semi-Synthetic 80W/90 gear lube. It took 3 different auto parts stores, Advance, Pep Boys and AutoZone they had 3 left, so I bought all three. I'm having a the same shop that rebuilt my 700/4 Hydramatic transmission last year. A real good experienced transmission and differential shop. The owner is going to do mine himself. I want to get new Bearing and seals pressed off and new ones on along with the differential install. sure hope it all works out, and I hoping this stops the popping noise I get sometimes going up a curb. And someone here mentioned that it would be a good idea to put some grease on the driveshaft yoke, so I'm going to have them put a dab in on the splines. Needless to say, No Royal Purple for me.
    Last edited by JTWard; 04-17-2014 at 05:47 AM.

  5. #5
    Jr. Apprentice
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    Sounds like you have had good advice and are on the right track. I know this isn't necessarily for you, but there are kits available (different clutches, springs etc) that can really "AMP" up "limited slip" aspect. On my hot-rod which I used to drag race...the car is in the air... if one person was able to hold onto one rear wheel and I rotated the other, the clutches & springs are so H-D that I promise the other person, no matter how strong, could stop the other tire from rotating! With drag racing coming out of the hole straight is critical, so that is one area one can not afford to compromise on.

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  7. #6
    Jr. Engineer JTWard's Avatar
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    Well Yeah, I got a good bit of info on differentials. I've always knew you had to put in the limited slip additive, But I never knew you could have too much if your using different types of gear oils. RP let me down, but at least I knew what is acceptable kind of gear lube. One guy said I was over thinking this whole differential fluid thing, and he is right. So I just bought the middle brand of Valvoline and I'm sure it will be fine. Sometimes I do , I get over involved in a project. I want perfect ! But sometimes I don't what perfect is, I'm ignorant in many ways and this is just one of them. I always try to think of any loose ends, and in many ways I just screw things up in obsession for the perfect way ?Attachment 58655

  8. #7

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    Valvoline should be fine. imo i found with oils sticking to the basic real oil works out better. normal oil last a diff around 200-300k miles. never gets changed. never really goes bad.
    94 sub 6inch lift 34inch bfg mt. massive rework project soon. the audio system hit 150.3db so now its time to rebuild and try for 155db. mudpuppy is also getting a new engine, rebuilt ifs, dual 500amp 15.1vdc alts, 5 5,000amp batts, ant the combined wattage with the new system should be close to 15,000watts. this is going to be a wild ride boy and girls.

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